U.S. patent number 8,696,101 [Application Number 13/364,778] was granted by the patent office on 2014-04-15 for photopolymerizable inkjet black ink, and ink cartridge, inkjet printer and printed material using the ink, and method of preparing the ink.
This patent grant is currently assigned to Ricoh Company, Ltd.. The grantee listed for this patent is Tomoko Hasegawa, Takao Hiraoka, Tsutomu Maekawa. Invention is credited to Tomoko Hasegawa, Takao Hiraoka, Tsutomu Maekawa.
United States Patent |
8,696,101 |
Hiraoka , et al. |
April 15, 2014 |
Photopolymerizable inkjet black ink, and ink cartridge, inkjet
printer and printed material using the ink, and method of preparing
the ink
Abstract
A photopolymerizable inkjet black ink having a viscosity not
greater than 20 mPas at 60.degree. C., including a clear ink having
a viscosity not greater than 15 mPas at 60.degree. C. including a
photopolymerizable monomer having a Stimulation Index (SI value)
less than 3 when subjected to a skin sensitization test (LLNA
method) and a polymerization initiator without including carbon
black and insolubles; and a carbon black in an amount not greater
than 7% by weight.
Inventors: |
Hiraoka; Takao (Kanagawa,
JP), Hasegawa; Tomoko (Ibaraki, JP),
Maekawa; Tsutomu (Kanagawa, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Hiraoka; Takao
Hasegawa; Tomoko
Maekawa; Tsutomu |
Kanagawa
Ibaraki
Kanagawa |
N/A
N/A
N/A |
JP
JP
JP |
|
|
Assignee: |
Ricoh Company, Ltd. (Tokyo,
JP)
|
Family
ID: |
46586290 |
Appl.
No.: |
13/364,778 |
Filed: |
February 2, 2012 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20120200648 A1 |
Aug 9, 2012 |
|
Foreign Application Priority Data
|
|
|
|
|
Feb 7, 2011 [JP] |
|
|
2011-024450 |
|
Current U.S.
Class: |
347/100;
106/31.29; 106/31.61 |
Current CPC
Class: |
C09D
11/101 (20130101); C09D 11/324 (20130101) |
Current International
Class: |
G01D
11/00 (20060101); C09D 11/00 (20060101) |
Field of
Search: |
;347/100
;106/31.29,31.61,31.62 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
101550295 |
|
Oct 2009 |
|
CN |
|
10-7968 |
|
Jan 1998 |
|
JP |
|
10-237367 |
|
Sep 1998 |
|
JP |
|
10-237368 |
|
Sep 1998 |
|
JP |
|
10-251589 |
|
Sep 1998 |
|
JP |
|
10-330663 |
|
Dec 1998 |
|
JP |
|
2002-20672 |
|
Jan 2002 |
|
JP |
|
2002-38072 |
|
Feb 2002 |
|
JP |
|
2003-55571 |
|
Feb 2003 |
|
JP |
|
3446213 |
|
Jul 2003 |
|
JP |
|
2005-344070 |
|
Dec 2005 |
|
JP |
|
2006-45511 |
|
Feb 2006 |
|
JP |
|
2006-257305 |
|
Sep 2006 |
|
JP |
|
2007-254700 |
|
Oct 2007 |
|
JP |
|
2008-248008 |
|
Oct 2008 |
|
JP |
|
2010-516860 |
|
May 2010 |
|
JP |
|
WO 99/67337 |
|
Dec 1999 |
|
WO |
|
WO 2007/126103 |
|
Nov 2007 |
|
WO |
|
WO 2008/091653 |
|
Jul 2008 |
|
WO |
|
WO 2008/091653 |
|
Jul 2008 |
|
WO |
|
Other References
Chinese Office Action issued Sep. 30, 2013, in China Patent
Application No. 201210023792.5. cited by applicant.
|
Primary Examiner: Lebron; Jannelle M
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier
& Neustadt, L.L.P.
Claims
What is claimed is:
1. A photopolymerizable inkjet black ink having a viscosity not
greater than 20 mPas at 60.degree. C., comprising: a clear ink
having a viscosity not greater than 15 mPas at 60.degree. C.,
comprising a photopolymerizable monomer having a Stimulation Index
(SI value) less than 3 when subjected to a skin sensitization test
(LLNA method) and a polymerization initiator without including
carbon black and insolubles; and a carbon black in an amount not
greater than 7% by weight.
2. The photopolymerizable inkjet black ink of claim 1, wherein the
carbon black has an adsorption layer formed of a polymeric
dispersant on its surface and the following relationship is
satisfied: 2d+h.ltoreq.1.1h wherein h represents an average primary
particle diameter of the carbon black; and d represents a thickness
of the adsorption layer.
3. The photopolymerizable inkjet black ink of claim 1, wherein the
photopolymerizable monomer is a compound selected from the group
consisting of polyethyleneglycoldimethacrylate having the formula
(1): ##STR00002## wherein n represents 9 or 14,
.gamma.-butyrolactonemethacrylate,
trimethylolpropanetrimethacrylate,
tricyclodecanedimethanoldimethacrylate, caprolactone-modified
dipentaerythritolhexaacrylate, caprolactone-modified
neopentylglycolhydroxypivalate ester, polyethoxylated
tetramethylolmethanetetraacrylate, ethyleneoxide-modified bisphenol
A diacrylate and hydroxyethylacrylamide.
4. An ink cartridge containing the photopolymerizable inkjet black
ink of claim 1.
5. An inkjet printer comprising the ink cartridge according to
claim 4.
6. A printed material printed with the photopolymerizable inkjet
black ink of claim 1.
7. A method of preparing a photopolymerizable inkjet black ink
having a viscosity not greater than 20 mPas at 60.degree. C.,
comprising: mixing a photopolymerizable monomer having a
Stimulation Index (SI value) less than 3 when subjected to a skin
sensitization test (LLNA method) with a polymerization initiator
without carbon black and insolubles to prepare a clear ink having a
viscosity not greater than 15 mPas at 60.degree. C.; dispersing the
photopolymerizable monomer, a carbon black and a dispersant to
prepare a dispersion; and diluting the dispersion with the clear
ink such that the resultant inkjet black ink includes the carbon
black in an amount not greater than 7% by weight.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This patent application is based on and claims priority pursuant to
35 U.S.C. .sctn.119 to Japanese Patent Application No. 2011-024450,
filed on Feb. 7, 2011, in the Japanese Patent Office, the entire
disclosure of which is hereby incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to a photopolymerizable inkjet black
ink, and an ink cartridge, an inkjet printer and a printed material
using the ink, and a method of preparing the ink.
BACKGROUND OF THE INVENTION
Photopolymerizable monomers for use in the photopolymerizable
inkjet ink include (meth)acrylic acid ester compounds, acrylamide
compounds, oxetane compounds, epoxy compounds, etc., and the
(meth)acrylic acid ester compounds and the acrylamide compounds are
preferably used because of being widely available in significant
quantities, and inexpensively and easily obtainable.
However, many of the (meth)acrylic acid ester compounds and the
acrylamide compounds are poisonous. Some of them have low oral
toxicity and skin irritancy, but those having low viscosity used
for the inkjet ink are not safe materials in skin sensitization,
occasionally causing contact allergy.
Meanwhile, methods of adsorbing a polymeric dispersant for well
dispersing a pigment such as carbon black in an inkjet ink are
known. In addition, many references such as Japanese published
unexamined applications Nos. 10-7968, 10-237367 and 10-251589
disclose specifying a molecular weight of the polymeric dispersant
for better dispersibility are known, but lowering viscosity is not
mentioned at all therein. As Einstein methods show, the viscosity
of a dispersion depends on a volume fraction of a pigment, and the
thickness of an adsorption layer needs to be as thin as possible to
prevent the volume of the pigment from increasing due to adsorption
of the polymeric dispersant. Even though the dispersant has a low
molecular weight, a thick adsorption layer is occasionally formed
unless adsorption of the polymeric dispersant is controlled,
failing in obtaining low viscosity.
Japanese published unexamined application No. 10-237368 discloses a
method of decreasing increase of viscosity when blending a pigment.
However, this needs a process of centrifugally removing an extra
polymeric dispersant, resulting in a complicated process of
preparing an ink.
Because of these reasons, a need exists for a low-viscosity
photopolymerizable inkjet black ink using a photopolymerizable
monomer safe in skin sensitization.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a
low-viscosity photopolymerizable inkjet black ink using a
photopolymerizable monomer safe in skin sensitization.
Another object of the present invention is to provide an ink
cartridge using the ink.
A further object of the present invention is to provide an inkjet
printer using the ink.
Another object of the present invention is to provide a printed
material using the ink.
A further object of the present invention is to provide a method of
preparing the ink.
These objects and other objects of the present invention, either
individually or collectively, have been satisfied by the discovery
of a photopolymerizable inkjet black ink having a viscosity not
greater than 20 mPas at 60.degree. C., comprising:
a clear ink having a viscosity not greater than 15 mPas at
60.degree. C., comprising a photopolymerizable monomer having a
Stimulation Index (SI value) less than 3 when subjected to a skin
sensitization test (LLNA method) and a polymerization initiator
without including carbon black and insolubles; and
a carbon black in an amount not greater than 7% by weight.
These and other objects, features and advantages of the present
invention will become apparent upon consideration of the following
description of the preferred embodiments of the present invention
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view illustrating an embodiment of the ink
cartridge including a case (exterior) of the present invention;
and
FIG. 2 is a schematic view illustrating an embodiment of the inkjet
printer of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a a low-viscosity photopolymerizable
inkjet black ink using a photopolymerizable monomer safe in skin
sensitization.
More particularly, the present invention relates to a
photopolymerizable inkjet black ink having a viscosity not greater
than 20 mPas at 60.degree. C., comprising:
a clear ink having a viscosity not greater than 15 mPas at
60.degree. C., comprising a photopolymerizable monomer having a
Stimulation Index (SI value) less than 3 when subjected to a skin
sensitization test (LLNA method) and a polymerization initiator
without including carbon black and insolubles; and
a carbon black in an amount not greater than 7% by weight.
The present inventors found some (meth)acrylic acid ester compounds
and acrylamide compounds usable as a photopolymerizable monomer
having a Stimulation Index (SI value) less than 3 when subjected to
a skin sensitization test (LLNA method). However, both of them have
high viscosities and need to be designed to prevent their
viscosities from increasing when mixed as an ink material. In
addition, a polymerization initiator needed for light curing of the
photopolymerizable monomer increases the ink viscosity, which
should be considered as well.
The LLNA method is a skin sensitization test specified as OECD test
guide line 429, and as shown on page 55 in "Functional Materials"
Vol. 25, No. 9 published in September, 2005, the skin sensitization
is determined to have no problem when Stimulation Index (SI value)
showing a degree of the skin sensitization is less than 3.
Further, material evaluated in MSDS (Material Safety Data Sheet) to
be negative in skin sensitization or have no skin sensitization,
obviously satisfying the SI value are included in the present
invention.
When a pigment is mixed in an ink, the viscosity thereof increases.
Therefore, something should be considered for preventing the
viscosity from increasing when a carbon black pigment is mixed
therein.
A solvent may be mixed to decrease the viscosity, but is preferably
not used because of having environmental and inkjet discharge
stability problems in consideration of its volatility.
Including the photopolymerizable monomer, the polymerization
initiator, but including neither carbon black nor insolubles such
as wax emulsion, an ink material (hereinafter referred to as a
clear ink) has a viscosity not greater than 15 mPas at 60.degree.
C. The resultant inkjet black ink (hereinafter referred to as an
ink) after mixed with carbon black has a viscosity as low as not
greater than 20 mPas at 60.degree. C. The maximum viscosity of inks
usable for marketed inkjet heads is 20 mPas at 60.degree. C., and
which needs satisfying.
In the clear ink, the photopolymerizable monomer works as a solvent
for the polymerization initiator. Namely, polymerization initiator
is dissolved in the photopolymerizable monomer.
The wax emulsion is an additive for strengthening the resultant
coated layer after polymerization, and when included too much
relative to the carbon black, the viscosity may not be
satisfied.
Specific examples of the photopolymerizable monomer having an SI
value less than 3 include polyethyleneglycoldimethacrylate having
the formula (1),
##STR00001## wherein n represents 9 or 14,
.gamma.-butyrolactonemethacrylate,
trimethylolpropanetrimethacrylate,
tricyclodecanedimethanoldimethacrylate, caprolactone-modified
dipentaerythritolhexaacrylate, caprolactone-modified
neopentylglycolhydroxypivalate ester, polyethoxylated
tetramethylolmethanetetraacrylate, ethyleneoxide-modified bisphenol
A diacrylate, hydroxyethylacrylamide, etc.
The ink includes carbon black in an amount not greater than 7% by
weight. This is because the resultant image density is equivalent
to that of the marketed inkjet black ink producing images having
the highest image density. The minimum quantity of the carbon black
is difficult to specify because the image density depends on
printers. Particularly, there have been some cases a very small
quantity of carbon black is mixed recently to produce pale color,
and may be properly determined according to applications.
The ink of the present invention can be discharged by marketed
inkjet heads and produces images having image density equivalent to
that of marketed inkjet black inks.
In the present invention, a polymeric dispersant is preliminarily
included in a carbon black dispersion to prepare an ink having a
specific low or lower viscosity, and in which the carbon black is
well dispersed.
Mixing the same photopolymerizable monomer as that used in the
clear ink, carbon black and a dispersant to prepare a carbon black
dispersion; and diluting the carbon black dispersion with the clear
ink to prepare the ink of the present invention. The clear ink
works as a dispersion medium of the carbon black.
In order to disperse carbon black in the clear ink, the polymeric
dispersant is effectively adsorbed on the surface of the carbon
black. It is necessary to form an adsorption layer having not less
than a specific thickness to obtain good dispersibility. When a
thick adsorption layer is formed on carbon black having a small
particle diameter, the volume of the carbon black largely
increases, resulting in larger viscosity.
Therefore, when a relationship 2 d+h.ltoreq.1.1 h, in which h is an
average primary particle diameter of carbon black and d is a
thickness of an adsorption layer formed if the carbon black on
which a polymeric dispersant is adsorbed, is satisfied, the present
invention can easily be prepared. In addition, the volume increase
of the carbon black when adsorbing the dispersant can be prevented,
and the resultant ink has a viscosity a not greater than 20 mPas at
60.degree. C. dischargeable by marketed inkjet heads.
2 d+h.ltoreq.1.1 h equals 20 d.ltoreq.h, and when a carbon black
having an primary particle diameter not less than 70 nm, an
adsorption layer having a thickness not less than 3.5 nm is formed.
When the adsorption layer has a thickness not less than 3.5 nm, the
carbon black is well dispersed.
The average primary particle diameter of the carbon black can be
measured by capillary viscosity measurement methods, dynamic light
scattering methods or measuring or observing with an electron
microscope.
As the polymeric dispersants, homopolymers or copolymers formed of
one or more monomers capable of forming polymers such as polyester
polymers, polyvinyl polymers, polyacrylic acid ester polymers and
polyurethane polymers, or these polymers having functional groups
such as amino groups, carboxylic groups, phosphoric groups,
sulfonic groups or their salts can be used. The polymeric
dispersants preferably have a molecular weight of from a few
thousand to hundreds of thousands. Marketed products include
Ajisper from Ajinomoto Fine-Techno Co., Inc., SOLSPERSE from The
Lubrizol Corporation, DISPARLON from Kusumoto Chemicals, Ltd.,
etc.
The ink of the present invention may include additives for
accelerating polymerizations such as sensitizers and polymerization
accelerators, polymerization inhibitors for preservation stability,
surfactants for assuring image quality, wax emulsions for assuring
coated layer strength after polymerization, etc.
Specific examples of the sensitizers include thioxanthone compounds
such as diethylthioxantone, isopropylthioxantone,
2-chloro-thioxanthone and 1-chloro-4-propylthioxantone; and
benzophenone compounds.
Specific examples of the polymerization accelerators include
tertiary amine compounds such as ethyl p-dimethylaminobenzoate,
ethyl hexyl p-dimethylaminobenzoate, benzoic
acid-2-dimethylaminoethyl and butoxy ethyl
p-dimethylaminobenzoate.
Specific examples of the polymerization inhibitors include phenol
quinone compounds such as hydroquinone, methoquinone, methyl
hydroquinone, t-butyl hydroquinone, di-t-butyl hydroquinone,
phenothiazine and 4-methyl-1-naphthol; and amine compounds.
Specific examples of the surfactants include fluoroalkyl
surfactants, dimethylsiloxane surfactants, alkyl surfactants,
etc.
Specific examples of the wax emulsions include polyethylene waxes,
carnauba waxes, fatty acid ester compounds, fluorine or
silicon-containing waxes, etc.
The ink of the present invention can be photopolymerized with light
irradiation not greater than 1,000 mJ/cm.sup.2.
Further, printed materials printed with the ink of the present
invention has high safety even when an unpolymerized monomer due to
process problems is left thereon because of its low skin
sensitization.
The ink of the present invention is preferably contained in a
cartridge. Thus, it is necessary to directly contact the ink, and
which prevents hands and clothes from being contaminated, and
filling the ink can be simplified.
The ink cartridge contains the ink in its container and has other
members when necessary. The container is not particularly limited,
and can select a shape, structure, size and materials, etc. in
accordance with the purpose. For example, ink bags formed of
aluminum-laminated films, resin films, etc. are preferably
used.
An embodiment of the ink cartridge (200) is explained, referring to
FIG. 1.
After an ink is filled in an ink bag (241) from an ink filling
opening (242) and the air therein is exhausted, the ink filling
opening (242) is heat-sealed to be closed. When used, a needle of
the apparatus is inserted an ink discharge opening (243) formed of
a rubber member to provide the ink to the apparatus. The ink bag
(241) is formed of a wrapping member such as aluminum-laminated
films having no air permeability. The ink bag (241) is typically
contained in a plastic cartridge case (244) as FIG. 1 shows, and is
detachably installed in various inkjet recorders.
The ink cartridge (200) contains an ink and can detachably be
installed in various inkjet recorders, and it is preferable that
the cartridge (200) is detachably be installed in the inkjet
recorder of the present invention mentioned later.
The inkjet printer of the present invention includes the ink
cartridge and a head discharging an ink.
Printing (discharging) methods include continuous spraying methods
and on-demand methods. The on-demand methods include piezo methods,
thermal methods, electrostatic methods, etc.
An embodiment of the inkjet printer of the present invention is
explained, referring to FIG. 2.
In FIG. 2, an ink cartridge 20 containing the ink for inkjet
recording of the present invention is contained in a carriage 18.
Plural ink cartridges 20 are contained, but do not need to be
plural. The ink for inkjet recording is fed to a droplet discharge
head 18a installed in the carriage 18 from the ink cartridge 20. In
FIG. 2, a discharge nozzle surface faces downward and is not seen,
but the ink for inkjet recording is discharged therefrom.
The droplet discharge head 18a installed in the carriage 18 is
moved by a timing belt 23 driven by a main scanning motor 26 while
guided by guide shafts 21 and 22.
Meanwhile, a specific coated paper (an image substrate) is placed
facing the droplet discharge head 18a by a platen 19. In FIG. 2,
numeral 1 is an inkjet printer, 2 is a chassis, 16 is a gear
mechanism, 17 is a sub-scanning motor, and 25 and 27 are gear
mechanisms.
Having generally described this invention, further understanding
can be obtained by reference to certain specific examples which are
provided herein for the purpose of illustration only and are not
intended to be limiting. In the descriptions in the following
examples, the numbers represent weight ratios in parts, unless
otherwise specified.
EXAMPLES
Preparation of Clear Ink
Clear inks A to G in Tables 1 to 1-1 were prepared by mixing
photopolymerizable monomers and polymerization initiators therein.
Their viscosities at 60.degree. C. are shown therein. Some monomers
having positive skin sensitization such as clear ink A have low
viscosities, but a few monomers having negative skin sensitization
have low viscosities.
However, clear inks B to K in Tables 1 to 1-1 having proper monomer
blending compositions have viscosities not greater than 15 mPas at
60.degree. C. The viscosities were measured by a cone-plate
rotating viscometer from Toki Sangyo Co., Ltd, setting the
temperature of a constant-temperature cyclic water at 60.degree.
C.
TABLE-US-00001 TABLE 1 A B C D E Photopolymerizable Positive
Neopentylglycol 100 Monomer skin diacrylate sensitization Negative
Polyethyleneglycol#400 5 skin dimethacrylate sensitization
Polyethyleneglycol#600 5 or SI value dimethacrylate less than 3
.gamma.-butyrolactone 5 methacrylate Trimethylolpropane 100 95 95
95 trimethacrylate Tricyclodecane dimethanol dimethacrylate
Caprolactone-modified dipentaerythritol hexaacrylate
Caprolactone-modified neopentylglycol hydroxypivalate ester
Polyethoxylated tetramethylolmethane tetraacrylate
Ethyleneoxide-modified bisphenol A diacrylate
Hydroxyethylacrylamide Polymerization initiator 2-methyl-1-[4- 20
20 20 20 20 (methylthio)phenyl-2- morpholinopropane-1- on Viscosity
at 60.degree. C. (mPa s) 8 14 13 14 13
TABLE-US-00002 TABLE 1-1 F G H I J K Photopolymerizable Positive
Neopentylglycol Monomer skin diacrylate sensitization Negative,
Polyethyleneglycol#400 no skin dimethacrylate sensitization
Polyethyleneglycol#600 or SI value dimethacrylate less than 3
.gamma.-butyrolactone methacrylate Trimethylolpropane 95 95 95 95
95 95 trimethacrylate Tricyclodecane 5 dimethanol dimethacrylate
Caprolactone-modified 5 dipentaerythritol hexaacrylate
Caprolactone-modified 5 neopentylglycol hydroxypivalate ester
Polyethoxylated 5 tetramethylolmethane tetraacrylate
Ethyleneoxide-modified 5 bisphenol A diacrylate
Hydroxyethylacrylamide 5 Polymerization initiator 2-methyl-1-[4- 20
20 20 20 20 20 (methylthio)phenyl-2- morpholinopropane-1- on
Viscosity at 60.degree. C. (mPa s) 15 15 15 15 15 15
Each of the photopolymerizable monomer used in the clear inks B to
K has the following SI values.
TABLE-US-00003 Polyethyleneglycol#400 dimethacrylate 1.3
Polyethyleneglycol#600 dimethacrylate 1.6 .gamma.-butyrolactone
methacrylate 2.1 Trimethylolpropanetrimethacrylate 1.9
Tricyclodecanedimethanoldimethacrylate 1.3 Caprolactone-modified
dipentaerythritolhexaacrylate Negative skin sensitization (from
MSDS) Caprolactone-modified neopentylglycolhydroxypivalate 0.9
ester Polyethoxylated tetramethylolmethanetetraacrylate 1.7
Ethyleneoxide-modified bisphenol A diacrylate 1.2
Hydroxyethylacrylamide No skin sensitization (from MSDS)
Examples 1 to 10, Comparative Examples 1 to 20 and Reference
Examples 1 to 3
The same amount of the photopolymerizable monomer used in each of
the clear ink A to K, 2% by weight of a polyester dispersant
including a basic functional group (a polystyrene-converted weight
average molecular weight 3,700), and 15% by weight of carbon blacks
having average primary particle diameters of 29 nm, 55 nm and 76 nm
were mixed to prepare dispersions.
The clear inks A to K were mixed in the relevant dispersions such
that each of the carbon blacks in the resultant ink has a content
of 7% by weight to prepare inks of Examples 1 to 10, Comparative
Examples 1 to 20 and Reference Examples 1 to 3 in Tables 2 to
12.
All of these inks could be polymerized with light irradiation not
greater than 1,000 mJ/cm.sup.2 and could produce images having
image density equivalent to those produced by the black ink for
Ipsio GX5000 from Ricoh Company, Ltd.
The average primary particle diameter of the carbon black, the
thickness of the adsorption layer of the dispersant, (2 d+h)/h, the
content of the carbon black, and the viscosity of the ink at
60.degree. C. are shown in Tables 2 to 12. The average primary
particle diameter was measured by electron microscope JEM-2010 from
JEOL Ltd.
The thickness of the adsorption layer of the dispersant was
determined by the following formula.
Thickness=(.phi.1-.phi.2)/pigment surface area wherein .phi.1 is a
volume fraction of a pigment (including the adsorption layer)
determined by Einstein methods (.eta.r=1+2.5.phi. wherein .eta.r is
a relative viscosity and .phi. is a volume fraction of the
pigment), and .phi.2 is a volume fraction of a known pigment, which
is previously weighed.
The viscosity of the ink at 60.degree. C. was measured by the same
method as that measured the clear ink.
Tables 2 to 12 show when 2 d+h is not greater than 1.1 h, carbon
black is mixed in clear ink having a viscosity of 15 mPas at
60.degree. C. in an amount of 7% by weight to prepare an inkjet
black ink having a viscosity not greater than 20 mPas at 60.degree.
C.
TABLE-US-00004 TABLE 2 Black ink based Comparative Comparative on
clear ink B Example 1 Example 2 Example 1 Average primary 29 55 76
particle diameter of carbon black (nm) Thickness of 3 3 3
adsorption layer of dispersant (2d + h)/h 1.21 1.11 1.08 Content of
carbon 7 7 7 black (% by weight) Viscosity at 25 22 19 60.degree.
C. (mPa s)
TABLE-US-00005 TABLE 3 Black ink based Comparative Comparative on
clear ink C Example 3 Example 4 Example 2 Average primary 29 55 76
particle diameter of carbon black (nm) Thickness of 3 3 3
adsorption layer of dispersant (2d + h)/h 1.21 1.11 1.08 Content of
carbon 7 7 7 black (% by weight) Viscosity at 24 21 18 60.degree.
C. (mPa s)
TABLE-US-00006 TABLE 4 Black ink based Comparative Comparative on
clear ink D Example 5 Example 6 Example 3 Average primary 29 55 76
particle diameter of carbon black (nm) Thickness of 3 3 3
adsorption layer of dispersant (2d + h)/h 1.21 1.11 1.08 Content of
carbon 7 7 7 black (% by weight) Viscosity at 25 22 19 60.degree.
C. (mPa s)
TABLE-US-00007 TABLE 5 Black ink based Comparative Comparative on
clear ink E Example 7 Example 8 Example 4 Average primary 29 55 76
particle diameter of carbon black (nm) Thickness of 3 3 3
adsorption layer of dispersant (2d + h)/h 1.21 1.11 1.08 Content of
carbon 7 7 7 black (% by weight) Viscosity at 24 21 18 60.degree.
C. (mPa s)
TABLE-US-00008 TABLE 6 Black ink based Comparative Comparative on
clear ink F Example 9 Example 10 Example 5 Average primary 29 55 76
particle diameter of carbon black (nm) Thickness of 3 3 3
adsorption layer of dispersant (2d + h)/h 1.21 1.11 1.08 Content of
carbon 7 7 7 black (% by weight) Viscosity at 26 22 19 60.degree.
C. (mPa s)
TABLE-US-00009 TABLE 7 Black ink based Comparative Comparative on
clear ink G Example 11 Example 12 Example 6 Average primary 29 55
76 particle diameter of carbon black (nm) Thickness of 3 3 3
adsorption layer of dispersant (2d + h)/h 1.21 1.11 1.08 Content of
carbon 7 7 7 black (% by weight) Viscosity at 29 24 20 60.degree.
C. (mPa s)
TABLE-US-00010 TABLE 8 Black ink based Comparative Comparative on
clear ink H Example 13 Example 14 Example 7 Average primary 29 55
76 particle diameter of carbon black (nm) Thickness of 3 3 3
adsorption layer of dispersant (2d + h)/h 1.21 1.11 1.08 Content of
carbon 7 7 7 black (% by weight) Viscosity at 27 23 20 60.degree.
C. (mPa s)
TABLE-US-00011 TABLE 9 Black ink based Comparative Comparative on
clear ink I Example 15 Example 16 Example 8 Average primary 29 55
76 particle diameter of carbon black (nm) Thickness of 3 3 3
adsorption layer of dispersant (2d + h)/h 1.21 1.11 1.08 Content of
carbon 7 7 7 black (% by weight) Viscosity at 28 23 20 60.degree.
C. (mPa s)
TABLE-US-00012 TABLE 10 Black ink based Comparative Comparative on
clear ink J Example 17 Example 18 Example 9 Average primary 29 55
76 particle diameter of carbon black (nm) Thickness of 3 3 3
adsorption layer of dispersant (2d + h)/h 1.21 1.11 1.08 Content of
carbon 7 7 7 black (% by weight) Viscosity at 27 23 20 60.degree.
C. (mPa s)
TABLE-US-00013 TABLE 11 Black ink based on Comparative Comparative
clear ink K Example 19 Example 20 Example 10 Average primary 29 55
76 particle diameter of carbon black (nm) Thickness of 3 3 3
adsorption layer of dispersant (2d + h)/h 1.21 1.11 1.08 Content of
carbon 7 7 7 black (% by weight) Viscosity at 60.degree. C. 26 22
20 (mPa s)
TABLE-US-00014 TABLE 12 Black ink based on Reference Reference
Reference clear ink A Example 1 Example 2 Example 3 Average primary
29 55 76 particle diameter of carbon black (nm) Thickness of 3 3 3
adsorption layer of dispersant (2d + h)/h 1.21 1.11 1.08 Content of
carbon 7 7 7 black (% by weight) Viscosity at 60.degree. C. 19 16
13 (mPa s)
* * * * *